The news agency Interfax quoted law enforcement sources claiming the explosions is a consequence of explosive substance placed in the carriage.

Photographs from the scene presented a metro train in the station with one set of doors blown out, and a number of people on the ground with harms. Eyewitnesses told people had to exit the carriage through the windows as the doors did not work.

Hundreds of people waited outside the station admission at street degree, along with fire engines and police vehicles.

The whole of the citys metro system was closed in the aftermath of the blast, and a number of streets at ground level were also shut off, as medical helicopters landed at the scene to evacuate the injured.

Russian chairwoman Vladimir Putin is in St Petersburg, where he spoke at a forum earlier in the working day. About an hour after the explosions, Putin carried his condolences to families of the victims before a meeting with the Belarus president, Alexander Lukashenko.

He said it was too early to say what made the explosions but that it could be offender or terrorist. Putin said he had already spoken with the director of the FSB security services and other law enforcement agencies.

Firefighters, emergency service vehicles and a helicopter near the station. Photograph: Peter Kovalev/ TASS

Since Russia entered the war in Syria, a number of Islamic State propaganda outlets have said the country would be a target. Nonetheless, there was no immediate claim of responsibility for the explosion.